From what I was aware when the story first showed, the kid walked onto the dogs territory and tried to take a bone from the dog. I think that's why people were going against the dog being PTS.

I think if the kid wandered off onto the dogs property and got bitten for reaching out to a strange dog, it isn't the dogs fault. But also the person babysitting the kid should have been watching out, especially if it was her dog. I'll re-read the story now to see if it's changed since the first time I read it.

Edit: I see now that the bone wasn't in the dogs mouth but on the floor..but either way I believe the kid shouldn't have been on the property?